Selective contact herbicidal compositions



2,805,927 Patented S p 1957 SELECTIVE CONTACT HERBICIDAL COMPOSITIONSPhilip C. Hannn, Webster Groves, Mo., assignnr to Monsanto ChemicalCompany, St. Louis, Mo, a corporation of Delaware No Drawing.Application July 11, 1955, Serial No. 521,389

7 Claims. (Cl. 712.7)

This invention relates to herbicidal compositions and more specificallypertains to selective contact herbicidal compositions containingthioacetamide as their essential active ingredient. This application isa continuation-inpart of the copending application Serial No. 296,254filed June 28, 1952, now abandoned.

In recent years numerous herbicidal compositions have been discoveredwhich greatly aid in the production of agricultural crops. In mostcases, these new compositions kill broad leaf plants but do not kill thegrasses such as the small grains and corn. Also, such compositions havebeen used to kill weed growth in plots of cultivated woody tissue plantswithout killing these Woody plants. Few herbicidal compositions havebeen discovered which will kill such obnoxious weeds as crab grass. Ingeneral, potassium cyanate or sodium arsenite are recommended for crabgrass control. Unfortunately, these compounds sometimes kill theperennial lawn grasses such as blue grass. The homeowners and groundkeepers of parks and golf courses have long sought a means foreradicating from the lawns which they care for the highly obnoxious crabgrass by some means other than digging up this Weed. Even when theserecommended crab grass killers are used at very low concentrations theyseverely injure the blue grass and make the treated turf unsightly.

It is an object of this invention to provide herbicidal compositionswhich will kill crab grass. It is also an object of this invention toprovide a composition which will kill crab grass but will not kill bluegrass. It is a further object of this invention to provide a selectivecontact herbicidal composition which is also useful in killing theterminal buds of certain crop plants.

The objects of this invention can be accomplished by the use ofcompositions containing thioacetamide as the essential active ingredientand a surface active agent admixed with a carrier. Such compositions areexceedingly useful for killing crab grass in blue grass lawns for theynot only do not kill the blue grass but they also appear to stimulatethe growth of the blue grass. These compositions can also be used todestroy apical dominance by 'killing the terminal bud of certain cropplants and per- The mitting the growth of auxiliary or secondary buds.above results can be achieved by the application of the compositionsofthis invention at a rate of from 4 to 70 pounds of thioacetamide peracre.

The preferred compositions of this. invention are those containing from0.5 to 10% by weight of thioacetamide and from 0.1% to 5% by weight of asurface active agent. These compositions can be prepared as liquidsprays employing an aqueous medium as a carrier, or by employinghydrocarbon oils as the carrier, or they can be prepared as sprayabledusts by employing finely-divided pulverulent solids as the carrier. Inany case, the compositions so prepared possess the common physical property of being in a flowable form in that they can be applied withspraying and dusting equipment. Accordingly, they all consist of theactive ingredient and the surface active agent incorporated in andadmixed with a fluent carrier.

The use of the term surface active agent herein is intended to includesuch compounds commonly referred to as wetting agents, dispersing agentsand emulsifying agents. The active agents which can be employed in thepreparation of the compounds of this invention are, for example, thosetypified by the following general classifi cations: sodium and potassiumsalts of fatty acids known as soft and hard soaps; salts ofdisproportionated abietic acid known as rosin soaps; salt of the hydroxyaldehyde acids present in seaweed known as algin soaps; alkalicaseincompositions; water-soluble lignin sulfonate salts; long chain alcoholsusually containing 10 to 18 carbon atoms; Water-soluble salts ofsulfated fatty alcohols con taining 10 to 18 carbon atoms; fatty acidesters of polyhydric alcohols; water-soluble salts of sulfated fattyacid amides; water-soluble esters of sulfated fatty acids; watersolublealkyl sulfonates having on the average of 16 carbon atoms in the alkylgroup; water-soluble aryl sulfonates; water-soluble alkyl arylsulfonates; Water-soluble aralkyl sulfonates; water-soluble sorbitanmono-laurates, palmitate, stearate, and oleate; condensation products ofethylene oxide with fatty acids, abietic acid, alkyl phenols andmercaptans; and others may be advantageously employed in preparing thecompositions of this invention. These dispersing and wetting agents aresold under numerous trade names and may either be pure compounds,mixtures of compounds of the same general groups or they may be mixturesof compounds of different classes.

The fluent compositions of this invention can be prepared in numerousways. For example, a simple aqueous sprayable composition can beprepared by dissolving from 0.5% to 10% by Weight of thioacetamide andfrom 0.1% to 5% by weight of a surface active agent in water. Thesesprays can also be prepared as aqueous colloidal dispersions oremulsions by dissolving the thioacetamide in the smallest amount ofwater immiscible organic solvent which will dissolve the quantity ofactive ingredient to be used and then colloidally disperse this solutionin water or preferably in an aqueous solution of a surface active agentby mechanical means, as with a homogenizer. Still another type ofaqueous spray formulation can be prepared by first dissolving the activeingredient in the smallest amount of a water immiscible organic solventwhich will dissolve the thioacetamide and then add this solution to anaqueous solution of a surface active agent.

Oil emulsions of thioacetamide can also be prepared. These compositionscan be prepared merely by emulsifying thioacetamide in a hydrocarbon oilwith a suitable surface active agent. The hydrocarbon oils which arepreferred for such formulations are the liquid hydrocarbon oilscontaining 10 to 20 carbon atoms. Specific hydrocarbon oils which areuseful for such formulations are the kerosenes, fuel oils, diesel oilsand the like.

In some instances it might be desirable to accomplish the purposes ofthis invention by the use of dusting compositions. Such compositions canbe conveniently prepared by thoroughly admixing thioacetamide and asurface active agent with afinely-divided pulverulent solid as thecarrier. Suitable materials for such carriers are clay, talc,diatomaceous earths, bentonites, and the like. A convenient method forthe preparation of such dust compositions is as follows: the desiredquantity of surface active agent is dissolved in a small quantity ofwater, to this aqueous solution there is added a sufficient quantity ofa pulverulent solid to form a rather thick paste, the paste is dried,finely ground added to the active ingredient, and the resulting mixtureball milled together until a homogeneous mixture is formed. This mixturecan then be diluted with additional quantities of pulverulent solidsuntil the desired concentration of the wetting agent and thioacetamideare obtained.

7 The following specific examples illustratespecific compositions ofthis invention as well as illustrating their, selective herbicidalactivity against crab grass. These tests were carried out in thegreenhouse with blue grass sod in flats of 300 square inches in area.Thersprays were applied with an atomizer at a volume rate ofr30 cc. perfiat.

- 7 Example I An aqueous solution was prepared containing 5% by weightof thioacetamide and 1.25% by weight of a liquid surface active agentcontaining about 65 by weight of the product of the condensation ofethylene oxide with abietic acid and about 35% by weight of an alkylamine salt of an alkylaryl sulfonic acid. This composition when sprayedon a bluegrass containing young 4 to 6 days old, crab grass plants atthe rate of 50 to 70 pounds of thioacetamide per acre gives a completekill of the crab grass in six days. There is but slight tip injury tothe blue grass but by the sixth day after treatment there was vigorousnew growth.

Example II The composition of Example I after dilution with additionalwater to a composition contaiing 4% by weight of thioacetamide and 1% byweight of the surface active agent when applied to a blue grasscontaining crab grass plants 4 to 6 days old at the rate of 40 to 56pounds of thioacetamide per acre results in a complete kill of the crabgrass in about seven days. The blue grass shows but very slight tipinjury a few days after treatment but by seven days after treatment,there is new vigorous growth.

Example 111 Aqueous compositions containing 3% by weight ofthioacetamide and 0.75% by weight of the surface active agent of ExampleI, 2% by weight of thioacetamide and 0.5% by weight of the same surfaceactive agent and a a composition containing 1% by weight ofthioacetamide and 0.25% by Weight of the same surface active agent wereprepared. These compositions applied at the rate of 10 to 40 pounds peracre produce very severe injury to young crab grass plants but killmature crab grass plants in six to eight days. The following test wasconducted with an established blue grass lawn.

Example IV Aqueous compositions containing 0.5 1.0% and 2.0% by weightof thioacetamide and about 1.0% by weight of the surfactant described inExample I were each sprayed on separate marked areas of established bluegrass sod containing young crab grass, before the fourth leaf appearedon the crab grass, at the rate of five pounds of thioacetamide per acre.Six days after treatment the in ry to the crab grass is very severe andresult in a kill of over 60%.

Portions of the treated areas were resprayed with the same compositionand at the same rate of application as the initial treatment and resultsin a substantially complete kill of the young crab grass plants.

Example V Dust compositions containing from 87% to 92% pulverulent solidsuch as Mississippi bentonite, 0.5% to 3% V 4 by weight of surfaceactive agent, such as described in Example I or sodium lauryl sulfate,and from 7.5% to 10% by weight of thioacetamide will kill both maturecrab grass and the young, more resistant, crab grass when applied at therate of 10 to 20 pounds of thioacetamide per acre.

Any of the other types of fluent formulations can be employed in thecontrol and eradication of crab grass from perennial grasses especiallyblue grass with results comparable to those described in theillustrative examples.

The specific formulations described and employed in the illustrativeexamples are not intended to be limiting, for as hereinbefore stated,the precise proportions of the ingredients can be varied, other surfaceactive agents can be substituted for those employed in these specificformulations and other fluent carriers can be employed where desired orwhen advantageous. variations are believed to be obvious to thoseskilled in the art.

7 What is claimed is:

1. A selective herbicidal composition comprising 0.5 to 10% by weight ofthioacetamide and from 0.1 to 5% by weight of a surface active agentadmixed with a finelydivided pulverulent carrier. 7

2. A selective herbicidal composition comprising an aqueous solutionconsisting of from 0.5% to 10% by weight of thioacetamide and from 0.1%to 1% by weight of a liquid surface active agent containing about byweight of the product of the condensation of ethylene oxide with abieticacid and about 35% by weight of an alkylamine salt of an alkylarylsulfonic acid.

3. The method of selectively killing crab grass growing in perenniallawn grass plots which comprises applying to said lawn grass plots acomposition comprising from 0.5 to 10% by Weight of thioacetamide andfrom 0.1% to 5% by weight of a surface active agent admixed with afluent carrier, at the rate of 4 to pounds of thioacetamide per acre.

4. The method of selectively killing crab grass growing in a blue grassplot which comprises applying to said blue grass plot a compositioncomprising from 0.5% to 10% by weight of thioacetamide and from 0.1% to5% by weight of a surface active agent in aqueous solution, at the rateof 4 to 70 pounds of thioacetamide per acre.

5. The method of selectively killing crab grass growing in a blue grassplot which comprises applying to said blue grass plot an aqueoussolution comprising from 0.5 to 10% by weight of thiocetamide and from0.1% to 1% by Weight of a liquid surface active agent consisting fromabout 65 by weight of the product of condensation of ethylene oxidationwith abietic acid and from about 35% by weight of an alkylamine salt ofan alkylaryl sulfonic acid, at the rate of 4 to 70 pounds ofthioacetamide per acre.

6. The method of selectively killing crab grass growing in a blue grassplot which comprises applying thioacetamide to said blue grass plot inan amount sufiicient to destroy the crab grass.

7. The method of selectively destroying crab grass growing in thepresence of perennial lawn grasses which comprises applyingthioacetamide in an amount suflicient to destroy the crab grass. 1

References Cited in the file of this patent UNITED STATES PATENTS2,604,409 Cothran July 22, 1952 These modifications and

3. THE METHOD OF SELECTIVELY KILLING CRAB GRASS GROWING IN PERENNIALLAWN GRASS PLOTS WHICH COMPRISES APPLYING TO SAID LAWN GRASS PLOTS WHICHCOMPRISES APPLYING TO TO 10% BY WEIGHT OF THIOACETAMIDE AND FROM 0.1% TO5% BY WEIGHT OF A SURFACE ACTIVE AGENT ADMIXED WITH A FLUENT CARRIED, ATTHE RATE OF 4 TO 70 POUNDS OF THIOACETAMIDE PER ACRE.